1. Field of the Invention
In general, the present invention relates to counterbalance systems for windows that prevent open window sashes from moving under the force of their own weight. More particularly, the present invention system relates to the structure of the brake shoe component of counterbalance systems for tilt-in windows.
2. Description of the Prior Art
There are many types and styles of windows. One of the most common types of window is the double-hung window. Double-hung windows are the window of choice for most home construction applications. A double-hung window consists of an upper window sash and a lower window sash. Either the upper window sash or the lower window sash can be selectively opened and closed by a person sliding the sash up and down within the window frame.
A popular variation of the double-hung window is the tilt-in double-hung window. Tilt-in double-hung windows have sashes that can be selectively moved up and down. Additionally, the sashes can be selectively tilted into the home so that the exterior of the sashes can be cleaned from within the home.
The sash of a double-hung window has a weight that depends upon the materials used to make the window sash and the size of the window sash. Since the sashes of a double-hung window are free to move up and down within the frame of a window, some counterbalancing system must be used to prevent the window sashes from always moving to the bottom of the window frame under the force of their own weight.
For many years, counterbalance weights were hung next to the window frames in weight wells. The weights were attached to the window sashes using a string or chain that passed over a pulley at the top of the window frame. The weights counterbalanced the weight of the window sashes. As such, when the sashes were moved in the window frame, they had a neutral weight and friction would hold them in place.
The use of weight wells, however, prevents insulation from being packed tightly around a window frame. Furthermore, the use of counterbalance weights on chains or strings cannot be adapted well to tilt-in double-hung windows. Accordingly, as tilt-in windows were being developed, alternative counterbalance systems were developed that were contained within the confines of the window frame and did not interfere with the tilt action of the tilt-in windows.
Modern tilt-in double-hung windows are primarily manufactured in one of two ways. There are vinyl frame windows and wooden frame windows. In the window manufacturing industry, different types of counterbalance systems are traditionally used for vinyl frame windows and for wooden frame windows. The present invention is mainly concerned with the structure of vinyl frame windows. As such, the prior art concerning vinyl frame windows is herein addressed.
Vinyl frame, tilt-in, double-hung windows are typically manufactured with guide tracks along the inside of the window frame. Brake shoe assemblies, commonly known as “shoes” in the window industry, are placed in the guide tracks and ride up and down within the guide tracks. Each sash of the window has two tilt pins or tilt posts that extend into the shoes and cause the shoes to ride up and down in the guide tracks as the window sashes are opened or closed.
The shoes contain a brake mechanism that is activated by the tilt post of the window sash when the window sash is tilted inwardly away from the window frame. The shoe therefore locks the tilt post in place and prevents the base of the sash from moving up or down in the window frame once the sash is tilted open. Furthermore, the shoes engage curl springs. Curl springs are constant force coil springs that supply the counterbalance force to the weight of the window sash. Brake shoes are designed to easily receive the tilt post of the window sash as the tilt-in window is being assembled at the factory. Unfortunately, many prior art designs that enable the brake shoe to receive a tilt post also make it possible for the tilt post to accidentally exit the brake shoe as a person manipulates the sash during tilting. If the tilt post exits the brake shoe, the brake shoe may retract to the top of the window track because of the force of the counterbalance springs. Alternatively, the tilt post may rest upon the top of a brake shoe rather than inside the brake shoe. This prevents the brake shoe from functioning properly. It also can prevent a window sash from closing properly. Both scenarios require that the tilt-in window be serviced before it will again function properly.
In the prior art, brake shoes have been designed with locking features that enable a tilt post to enter the brake shoe, but prevent that tilt post from inadvertently exiting the brake shoe. Such prior art brake shoe designs are exemplified by U.S. Pat. No. 5,243,783 to Schmidt, entitled Locking Slide Block, and U.S. Pat. No. 6,658,794 to Hansel, entitled Guide Assembly For A Tilt-Out Sash Window. Such prior art designs require that catch locks be assembled into the structure of the brake shoe. This complicates the structure of the brake shoe, thereby making the shoe impractical to mold as a single piece. Rather, the brake shoe must be manufactured as a multi-part unit that must be assembled before it can be utilized in the structure of a tilt-in window. This adds significantly to the costs associated with producing and installing brake shoes. Furthermore, the presence of the catch lock complicates the removal of the sash from the window frame when the sash needs to be removed or replaced. Often the catch lock must be removed from a brake shoe using tools. In such a situation, a serviceman or homeowner would rarely reinstall the catch lock after it is removed. From that point onward, the tilt posts within the window are at risk of inadvertently separating from the brake shoes and disabling the functionality of the window.
A need therefore exists in the field of vinyl, tilt-in, double-hung windows, for a counterbalance system with a brake shoe that can actively retain a tilt post, yet remain both simple and inexpensive to manufacture. A need also exists for a brake shoe that actively retains a tilt post, yet can be caused to release a tilt post without tools or disassembly. These needs are met by the present invention as described and claimed below.